ecobin Loc: Paoli, PA

Ballard, your work is outstanding! I always look forward to your posts.

alberio Loc: Casa Grande AZ

Deep in the Heart of Trifid. Another job well done.

jaymatt Loc: Alexandria, Indiana

Interesting.

JBRIII

If I am correct, you took no luminance photos correct?, just the three narrow band sets? I ask for two reasons: I haven't noticed this being done by others in published photos, and have wondered why not, maybe I've just missed it.
Second, this opens up two possibilities of interest, a. use more narrow band filters in a wheel instead of three RGB and one luminance filters. b. use an older type achromatic objective (cheaper than new LD glass), but change the focus between filters to eliminate residual chromatic abberation.

Thanks;
Jim

Earnest Botello Loc: Hockley, Texas

Great captures, Ballard.

Ballard Loc: Grass Valley, California

Hi malawibob
Thanks for checking out the photo of the Trifid nebula with narrow band filters, and the comment. To keep the stars from moving during the exposure the 16 inch telescope I used to take the image is mounted on an Astro-Physics 1600GTO mount that is polar aligned and tracks with the earths movement. For fine guiding due to atmospheric refraction and any periodic error in the mount I used an off-axis guider with a small CCD that monitors a star every 2 seconds and passes the info to my laptop which then sends minor corrections to the mount to keep the image stationary during the exposures. Between each shot the computer also moves the mount very slightly between shots (known as drizzling) so the each shot is a couple of pixels different than all the others (this helps prevent any bad pixels for being in the same spot on the image when the images are realigned in software and will average them out (You end up losing a couple pixels all around the edge of the shot but this is insignificant for the final image).

Ballard Loc: Grass Valley, California

Hi ecobin
Thanks for viewing the narrow band image of M20 and for the comment.

Ballard Loc: Grass Valley, California

Hi J-SPEIGHT
Thanks for checking out my latest image of the Trifid nebula and for the comment.

Ballard Loc: Grass Valley, California

Hi alberio
Thanks for viewing the narrow band image of the Trifid nebula and for the comment. As always I still learning how to do this stuff.

Ballard Loc: Grass Valley, California

Hi Jaymatt
Thanks for checking out my newest image of the Trifid nebula and for the comment. The narrow band image dims out the star image but brings out different detail compared to the DSLR image.

Ballard Loc: Grass Valley, California

Hi JBRIII
Thanks for checking out my narrow band image of the Trifid nebula and for the question and comment. Your are correct I didn't take a luminance set of frames in this case. I'm still learning how to do this stuff but I found from my first try with all narrow bad (See pillars of create shot at https://www.uglyhedgehog.com/t-703834-1.html )
that adding luminance tended to mute some of the details brought out with the narrow band only so and I didn't use the luminance on either of my narrow band shots so far. But I have found that using Ha with LRGB works well with the Ha added to the red particularly to bring out nebula knots in the arms of galaxies.
The narrow band works well to only allow specific frequencies so that it removes most light pollution and to a great extent moon light. In fact you can see that it removes and dims a lot of the stars also, but brings out the nebula (assuming it has the correct elements).
I expect that you are correct in that you could remove some chromatic aberration with filters, you may need to change the image scale slightly for the shots since moving the focus to perfectly focus a given color would necessarily change the effective focal length and therefore the image size. I expect you could this with just RGB (no luminance). If you choose narrow band filters that are all in a fairly close frequency you could probably avoid the refocus and create an interesting false color image. For black and white images I expect a just a regular red filter would work to remove the color fringes seen with less expensive refractors.

Ballard Loc: Grass Valley, California

Hi Earnest Botello
Thanks for checking out my latest all narrow band astro-photo and for the comment.

jimvanells Loc: Augusta, GA

Great set of images!

Ballard Loc: Grass Valley, California

Hi jimvanells
Thanks for checking out the narrow band images of the trifid nebula and for the comment

JBRIII

Thanks for the reply;
I agree on the image size and don't know how much change there would be from the UV to IR, and should be correctable in software before merging. I am just thinking about things at this point. But for example, a single quartz objective would allow observing from UV out. Admittedly, the amount of UV is low, better at high altitudes, but might be possible, where normal glass absorbs a lot of what there would be. Certainly some UV work is possible as shown by Vensus filters. Also, quartz is better for work beyond 1100 nm, needs a different camera.

Finally, I just found out that the spectrohelioscope at Stellafane has an objective adjustment so other than H-alpha czn be observed.

Your image looks good, so obviously, narrow band alone is fine, and as you state certainly helps with the moon. I have a Stellena, which has a pollution filter built in, but the moon is still very problematic.

Thanks for responding and listening;
Jim